FIG. 4 is a perspective view showing a prior art chip type LED. The chip type LED 1 includes an insulating substrate 2 in the form of a chip, a pair of terminal electrodes 3 and 4 formed on an upper surface of the insulating substrate, and a light emitting diode chip 5 mounted on the terminal electrode 3 with the anode electrode 5b oriented upward and the cathode electrode 5a oriented downward for electrical connection to the terminal electrode 3. The anode electrode 5b is electrically connected to the terminal electrode 4 by e.g. wire bonding using a non-illustrated thin metal wire. A transparent package 6 for hermetically sealing the light emitting diode chip 5 is provided on the upper surface of the insulating substrate 2 (See Patent Document 1).
Conventionally, when a plurality of chip type LEDs having the above-described structure is used as a backlight source for key switches arranged in matrix in a cell phone A, the chip type LEDs 1 are arranged on a circuit board C below the key switches B at positions between the key switches B, as shown in FIG. 5. With this arrangement, the key switches B are illuminated with the light emitted laterally from the side surfaces of the packages 6 of the chip type LEDs 1.
Patent Document 1: JP-A-H10-50734